He will probably think girls his own age need a few lessons, that is about is far as it will go for him.But there is an innocent angel underneath all that testosterone. While he undoubtedly enjoyed the temporary physical pleasure he received by being used by an adult female for her gratification, it was a shallow experience that certainly can't be a postive experience for his entire manhood.
Do you never weigh the emotional impact of sex ?
He was using her, just as much as she was using him. I also highly doubt he would have looked back on it as a negative experience, he probably will now because he got caught, but he had not he probably wouldn't have. Do you not know men? or even women?
If you are going to do something like that in the first place, I doubt you would see it as a negative.
There is no way for you nor anyone else to know what kind of impact this will have on as he matures. What will he think of women or himself as the result of this experience is an unknown. Society draws some lines for reasons and in spite of your experiences, men are not totally comprised of testosterone. Expecting them to be can sure encourage that behavior tho.